Method of and apparatus for the reduction of granular materials



Jan. 29, 1935. G1 HAIQIN 1,989,615

METHOD OF AND APPARATUS FOR THE REDUCTION OF GRANULAR MATERIALS I FildNOV. 10, 1930 INV ENTOR GEO/Egg L. HAN/v.

BY i z 0 ATTORNEY Patented Jan. 29, 1935 I METHOD OF AND APPARATUS FORTHE DUCTION F GRANULAR MATERIALS George L. Hann, New Brighton, StatenIsland, N. Y., assignor to United States Gypsum Company, Chicago, 111.,a corporation of Illinois Application November 10, 1930, Serial No.494,471

3 Claims. (01. 83-94) r This invention relates to the reduction of the amethod and apparatus for-eliminating any dust particle size of powderedmaterials and has refnuisance incident to the operation of tube anderence more particularly to a method of and apball mills operating uponcalcined gypsum.

paratus for the reduction of-such powdered. ma Reference is to be had tothe accompanying 5 terials as calcined gypsum, in tube mills or balldrawing forming a part of this specification, in 5 mills. which Inthe'manufacture of calcined gypsum, such Fig. 1 is a plan view of aplant layout of tube as the products commonly called first settle andmil s mb y n my mpr v d St v l (1 second settle stucco, it is standardpractice to calvice and 0 cine the gypsuminakettle, and while the gypsumFig. 2 is an end elevation par y in Section Of 10 is still hot from thecalcination, it is transferred the devices shown in Fig. 1. v to buhrmills for an initial grinding operation. One or more tube mills 10 ofstandard design, The friction of grinding serves to maintain the may beprovided for grinding calcined gypsum temperature and prevent thecalcined -gypsum or other powdered material, which is admitted fromcooling down, and while in this hot state of through the hollow shaft atone end'of the tube 15 325 to 350 F. it is transferred to tube or ball vmill by a hopper or chute 11 having at its lower mills where thefineness is again considerably inend, a screw conveyor 12 operated frommotor 13 creased for certain uses. During the tube millthrough a speedreducer 14 so as to cause a steady ing operation, a considerable amountof steam is stream of the powdered material containing an formed fromthe excess of water contained in the excess of moisture, to continuouslyenter the tube 20 calcined gypsum, and if this. steam is not removedmill for grinding. The rotation of the tube mill from the tube mill, theresulting calcined gypsum 10 may be caused by -means of a large gear 15does not keep very well and. sufiersapartial rehy-' meshing with apinion 16 secured to any suitdration upon storing for prolonged periods,possiable powed shaft 1'7, the latter being rotatably bly duetotheretained and condensed water again mounted in bearings 18. 25recombining with the calcined gypsum. The high A housing 19 is formedaround the hollow shaft temperature in the .tube mill is maintained .byat the delivery end of the tube mill l0, and a reason of the heat offriction generated within chute 20 leads to a screw conveyor housing 21the tube mill. Failure to remove this steam from having therein ahelical conveyor 22 for continthe tube mill, also makes it diflicult tocontrol uously removing the powdered material from the 30 the settingtime of the calcined gypsum, and as a tube mill after grinding. I mayconnect a duct result the working qualities of the calcined gyp- 23 toany suitable part of the system for withsum for plaster or otherplastics are not good and drawing the steam generated during thegrindare not uniform. If the steam is not removed ing operation, but forthe purpose of illustration, I

from the tube or ball mill, a certain amount of I have shown this ductas connected to the de- 35 condensation may take place in the conveyinglivery housing 19. This duct preferably extends equipment which removesthe calcined gypsum upwardly at an angle of about 45 degrees and fromthe tube or ball mill, and this condensed then downwardly to form ashort duct leg 24 and moisture causes a corrosion of the conveying thena long duct leg 25, with a removable cleanequipment with resulting highmaintenance cost. ing cap 26positioned at the apex of the duct legs 40.The tube mills and ball mills may also create an 23 and 24. A damper 27having a control handle objectionable dust nuisance if the dust is notprop- 28 is preferably provided in the duct leg 24 so as erly taken careof. to control the volume of steam removed from the An object of thisinvention, therefore, is to tube mill.

provide a process of and apparatus for removing The lower ends of theducts 25 are preferably 45' steam generated in a tube or ball milloperating connected to a horizontally extending manifold upon calcinedgypsum or other powdered mate- 28 which may be closed at one end with acap 29, rial, so that the qualities of the resulting prodand is providedat the other end with an elbow nets are maintained at a high level. 30,the long arm of which extends vertically and Another object of theinvention is to provide a is closed at the top by means of aremovableclean- 50 method of removing steam Item the tube or ball ing cap 31. Thelower end of the elbow arm 30 mills so that the condensation ofmoistureis preis connected by pipe 32 to a sump 33 having, an I ventedin conveying equipment with the resultoutlet pipe 34 near its bottom fordischarging ing elimination of corrosion. waste wash water. The pipe 34preferably ex- A further object of the invention is to provide tendsunderneath the surface 35 or a body of 55 water and a pipe 36 leadsupwardly from the sump 33 to the suction side of an exhaust fan 37 whichdischarges into the open air through a vertical stack 38. By balancingthe speed of the exhaust fan 37 against the height of the sump 33 abovethe body of water 35, the level 39 of water in th sump 33 is usuallymaintained above the outlet pipe 34 due to the partial-vacuum created inthe system so that all of the uncondensed gases go up the pipe 36 andthrough the exhaust fan 37 to stack 38. The pipe 41 and apparatus belowsaid pipe, may conveniently be located below the floor level 4'7. V

In order to remove any dust particles contained in the steam escapingthrough the manifold 28, and to aid in creating a suction or particalvacuum on the tube mill, I provide a water supply line 41 having aseries of downwardly extending pipes 42 connected to the upperside ofthe manifold 28. Each of these pipes 42 has a nozzle 43 of standarddesign at its lower end which is preferably directed at an angle ofabout 30 to the axis of the manifold 28 so that a spray of water passesfrom said nozzle when avalve 45 on line 41 is opened. These sprays ofwater serve to direct the vapors, steam and gases along the manifold 28to the right, as seen in Fig. 2, and on reaching the elbow arm 30,another spray of water is directed onto the gases by means of. a pipe 46passing through thecap 31. Upon reaching the sump 33, the mixture ofwater and uncondensed gases separates, the water going out of the drainpipe 34 and the gases going up the pipe 36 to the exhaust fan 37.

In operation, the hot, powdered calcined gypsum passes down the hopperl1, and is continuously moved by screw conveyer 12 into the tube mill10. A continuous discharge of finely ground,

hot material takes place into the housing 19 and out duct 20 into theconveyor housing 21, being moved continuously along said housing 21 to adischarge point. Exhaust fan 37 continuously draws steam and vapor fromthe interior of the tube mill through ducts 23, 24, 25, manifold 28,elbow arm 30, pipe 32, sump 33 and pipe 36, and forces the uncondensedgasesinto the stack 38. Water passesthrough pipe 41 when valve 45 isopen, and then passes through branch pipes 42 and the top of themanifold 28, and out through spray nozzles 43. The sprays of water causea condensation of the steam drawn from the tube mills, the waste watercollecting in the sump 33,

and then passing out through drainpipe 34 into the body of water 35. Theuncondensed gases pass out through pipe 36, exhaust fan 37 and into thestack 38.

I would state in conclusion that while the illustrated exampleconstitutes a practical embodiment of my invention, I do not wish tolimit myself precisely to these details, since manifestly, the same maybe considerably varied without departing from the spirit of theinvention as defined in the appended claims.

Having thus described my invention, I claim as new and desire to secureby Letters Patent:

1. The method of tube-milling calcined gypsTim, which comprisescontinuously introducing coarsely ground hot calcined gypsum into a tubemill, reducing said gypsum to a nne powder by the operation of said tubemill, continuously discharging the finely ground material from said tubemill,

withdrawing steam from said tube mill during the grinding operation bythe application of a partial vacuum to said tube mill, spraying thesteam withdrawn from said tube mill with water to condense the steam andseparate out fine particles of the gypsum, collecting the water andparticles of gypsum, and discharging the gases uncondensed by said waterspray..

2. The combination with a plurality of tube mills for continuouslyreceiving hot, coarsely ground, calcined gypsum and grinding saidgypsum, and means for discharging said finely ground, hot, calcinedgypsum continuously, of outlet ducts for withdrawing steam and vaporsliberated by the grinding of said gypsum connected to said tube millsadjacent the discharge ports thereof, a manifold connecting said outletducts, means for spraying water in said manifold so as to wash the steamand vapors withdrawn from said tube mills, and means for collecting anddischarging the wash water separated from the uncondensed gases.

3. Apparatus adapted for withdrawing and disposing of dust and moistureladen gases from disintegrators or the like, comprising a withdrawalduct, an exhaust fan, a passage connecting said duct and fan, a waterspray in said passage for washing the gases and removing the dust andmoisture therefrom, and means for collecting said dust and water anddischarging the water separated from the uncondensed gases.

GEORGE L. HANN.

